It is known to supply water to flue gases, e.g., originating from incinerator plants, to lower the flue gas temperature or to reduce the amount of discharged substances harmful to the environment. To achieve this object, water or an aqueous solution is sprayed into the flue gases, if required after a preceding treatment of the gases in a fluidized bed. By withdrawing the heat required for evaporation, the temperature of the flue gases decreases, which results in less thermal load on the environment. This temperature drop is often also required in connection with an optional subsequent treatment of the flue gases, e.g., a filtration. The filtration equipment is often not resistant to the temperature of untreated flue gases.
It is common practice to spray water or an aqueous solution into flue gases by means of sprayers, which may be of different types. It is known, for instance, to use two-phase sprayers, such as ultrasonic sprayers. It is also possible to use sprayers based on the spraying effect of a liquid supplied under high pressure.
The use of different types of sprayers often results in the problem that corrosion and/or erosion wears the sprayers rapidly. When sprayers are used for treating flue gases having a temperature close to the acidic dew point of the flue gases, those parts of the sprayers contacting the flue gases under conditions of condensation will easily corrode. This is especially the case with flue gases having a relatively low temperature. Corrosion may also occur in the case of condensation of acidic constituents of the flue gases on metal parts of the sprayers as a result of the low temperature of these metal parts. It is possible to partly solve this problem by using expensive, corrosion-resistant materials, such as nickel steel and the like. However, this entails very high cost, while the problem is not adequately solved though.
During treatment of flue gases contaminated with solids, e.g., as a result of a preceding treatment in a bed of solid particles, such as a fluidized bed, erosion of the spray head often occurs owing to a reduced pressure formed near the spray head, which results in that solids from the flue gases are drawn to the head.
There is therefore a need for a spraying system less sensitive to corrosion caused by the acidic constituents of the flue gases to be treated. There is also a need for a spraying system less sensitive to erosion of the spray head.